Window installation parts.

Getting to the point I can put all the side glass back in the car. There are supposed to be what looks like bushings, maybe plastic or nylon, that go thru some large holes in the door glass that hold the glass in place. All I have left is a part of one of em. Not sure what they are actually called and am having a heck of a time searching because of that. Haven't even looked at the back one yet, I'd assume there is something similar there.

What are these called (and any good places to find em) ?

'74 Dart Swinger